Food patties of various kinds, including hamburgers, molded "steaks", fish cakes, poultry patties, pork patties, and various vegetable patties are frequently formed in high volume automated molding machines. Patty molding machines adaptable to any of these food products which have proven quite successful are described in Richards Reissue U.S. Pat. No. Re. 30,096 reissued Sept. 18, 1979, Sandberg et al U.S. Pat. Nos. 4,054,967 issued Oct. 25, 1977, and Lamartino et al 4,182,003 issued Jan. 8, 1980.
Although any of those machines, and others as well, are capable of producing food patties of consistent size, weight, and configuration on a high volume basis, substantial problems may be encountered when the machines are required to mold patties from food products which, unlike hamburger, have not been ground to relatively small particle size. Thus, in many instances it may be desirable to form food patties from a food product that has not been chopped or ground into a consistent small particle material. For example, it may be desirable to mold food patties from a starting material consisting of whole poultry breasts, large segments of pork or other meat, or large fish filets. In this specification and in the appended claims, a food product of this kind is referred to as a "whole fiber food product".
A molding mechanism that solves some of the problems encountered in molding food patties from a whole fiber food product is described in Sandberg et al U.S. Pat. No. 4,356,595 issued Nov. 2, 1982. In one form of the molding mechanism described in that patent, using a plural cavity mold plate disposed in close-fitting relationship between planar surfaces of a fill member and a cover member, the food product is pumped into mold cavities in the mold plate through aligned fill apertures in the fill member. The fill apertures are preferably matched in size and configuration to the mold cavities. However, even that molding mechanism presents some technical problems in its operation when employed to mold patties from whole fiber food products.
In a molding mechanism of this kind, the total clearance between the mold plate and the adjacent cover member and fill member is only about 0.001 inch to 0.003 inch (0.025 cm. to 0.076 cm.). When the food product is pumped into the mold plate cavities it is under relatively high pressure; the pumping pressures may be as high as 400 psi (28 Kg/sq. cm.) in the machine of the Richards patent, 220 psi (15.5 Kg/sq. cm.) in the mechanism of the Lamartino patent, and 250 psi (17.6 Kg/sq.cm.) in the Sandberg et al U.S. Pat. No. 4,054,967. This high pressure tends to force the mold plate into firm contact with the cover member, leaving all of the available clearance as a minute space between the mold plate and the fill member. When the mold plate moves from its fill position toward its discharge position, fibers of the food product tend to be pulled into this very limited space between the mold plate and the fill member, trailing behind the mold cavity. When the knockout or discharge cups are moved through the mold plate cavity to discharge the molded food patties, these trailing fibers, still trapped at their extremities between the mold plate and the fill member, tend to function as a hinge. This hinge effect causes irregular registration of patties on the takeaway conveyor and may even pull the patties apart, leading to difficulties at subsequent processing stations. The trailing fibers also detract from the final appearance of the patties.
Another problem encountered in the molding of food patties from whole fiber food products occurs because large portions of the food product may tend to bridge the portions of the fill member between the fill apertures. When this occurs, the bridging portion of the whole fiber food product is torn as the high pressure pumping action forces it into the fill apertures and then into the mold cavities. This tearing action destroys the fibrous integrity of the product and may have a noticeable adverse effect on the texture of the molded patties.
One expedient that has been used to ameliorate both of these problems has been to chill the whole fiber food product before it is introduced into the food patty molding machine. However, chilling is relatively expensive and tends to reduce the operating efficiency of the molding machines. Furthermore, if the chilling is sufficient to partially freeze portions of the product, which is often the case, damage to the cellular integrity of the food product may occur with a resultant adverse effect on the texture for the molded patties.